期刊
EARTH AND PLANETARY SCIENCE LETTERS
卷 217, 期 3-4, 页码 237-244出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/S0012-821X(03)00609-5
关键词
isua; oxygenic photosynthesis; carbon; Archaean; Ph isotopes; U; Th
> 3700 Ma metamorphosed pelagic shale from West Greenland contains up to 0.4 wt% reduced carbon with delta(13)C values down to -25.6parts per thousand [PEB, PeeDee Belemnite]. The isotopic signature and mode of occurrence suggest that the carbon derived from planktonic organisms. The Pb isotopic composition shows that the shale had high primary U/Th. This indicates that organic debris produced a local reducing environment which precipitated U transported to the site of sedimentation by oxidized ocean water. The existence of highly productive plankton that fractionated C isotopes strongly and set up oxidation contrast in the environment suggests that oxygenic photosynthesis evolved before 3700 Ma. (C) 2003 Elsevier B.V. All rights reserved.
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